An engine used in a construction machine is required to meet various regulations and standards. One of the standards is to decrease contaminants, such as nitrogen oxide (NOx) and a particulate matter (PM) contained in exhaust gas, which may serve as a significant environment standard, together with regulations on a noise, in using the construction machine.
In order to comply with the environment standard, an engine adopting various means, such as an exhaust gas recirculation (EGR) apparatus and a diesel particulate filter (DPF) apparatus, has been typically used.
Here, the DPF refers to a filter capable of collecting and filtering soot that is a particulate matter including exhaust fumes on a path, for example, within a muffler, through which exhaust gas discharged from the engine is discharged, and may also refer to a device on which the aforementioned filter is mounted. Hereinafter, the diesel particulate filter will be abbreviated as the DPF.
The filter requires a process of removing soot collected therein periodically or arbitrarily according to the amount of collected soot, which is typically referred to as a “DPF regeneration” or a “combustion and removal”.
The regeneration may be generally divided into a passive regeneration and an active regeneration according to an implementation method thereof.
For example, a passive DPF regeneration refers to a method in which soot collected inside a filter is combusted by an increased temperature of exhaust gas while operating a construction machine, or a small amount of fuel is injected into a path through which exhaust gas is discharged during an operation of a construction machine, so that a diesel oxidation catalyst (DOC) apparatus disposed on the path in advance and the injected fuel generate an exothermic reaction to generate higher heat, thereby combusting collected soot.
Next, an active DPF regeneration refers to a method in which exhaust gas is discharged by actively driving an engine of a construction machine without requiring substantial work to be performed by a driver, and a small amount of fuel injected into an exhaust path based on a temperature of the exhaust gas also generates an exothermic reaction with a DOC apparatus disposed on the exhaust path in advance, so that a temperature of the exhaust gas is further increased to a temperature necessary for combustion (regeneration) of soot, thereby combusting the soot collected inside a filter.
A schematic configuration of a typical active DPF regeneration system will be described with reference to FIG. 1 below.
Referring to FIG. 1, the typical active DPF regeneration system 100 includes an engine 10 provided with a turbo charger 12, a DPF 30 provided on an exhaust path 20 through which exhaust gas discharged from the engine is discharged, and a DOC apparatus 40 at a front end of the DPF, and further includes a fuel injection means 50 for injecting a small amount of fuel into a front end of the DOC in the exhaust path 20, and a pump 60 driven by the engine 10.
In a case of the active DPF regeneration, substantial work load is not generated, so that details thereof will be omitted in the drawing.
In a case of the active DPF regeneration with the system having the aforementioned configuration, since a construction machine is in an operation stopped state, the active DPF regeneration maintains a state where substantial work of the construction machine, such as driving a front work means, such as a boom and a bucket, and driving a vehicle in front and rear directions, is not generated, and an engine is driven in an idle state (that is, low rpm) receiving a minimum load, and thus a temperature of exhaust gas discharged in the idle state is not easily increased.
That is, the exhaust gas discharged from the engine, which beings to be driven in the idle state, has a relatively low temperature, compared to a temperature while being operated.
In the meantime, in order to combust (DPF regenerate) soot collected inside the DPF by the active DPF regeneration method, an exothermic reaction needs to be generated between the DOC disposed on the exhaust path and fuel injected into the exhaust path at the front end of the DOC, and the exothermic reaction is available at a predetermined temperature (approximately 235° C.) or higher, so that in a case of the active DPF regeneration performed without substantial work load, a considerable time is required until the exhaust gas is heated to the predetermined temperature.
The engine generally discharges exhaust gas with a higher temperature in a case where the engine is driven by receiving a load, compared to a case where the engine is driven in an idle driving state. However, since the engine is driven in a substantial no-load state (idle state) in a state where the construction machine is stopped in the active regeneration contrary to the passive regeneration, a considerable time is demanded until the temperature of the exhaust gas is increased to a predetermined temperature at which an exothermic reaction of the DOC is available. For example, it is known that in a case of the active DPF regeneration of the construction machine, approximately 30 minutes to one hour is taken.
Since purchase cost of the construction machine is large, most of the construction machines are generally rented based on hours or days, and contrary to the passive DPF regeneration process, which is capable of being carried out with work, the active DPF regeneration process, which needs to spend a predetermined amount of time without performing an operation, this adds to a cost burden in renting the construction machine.
In addition, even in a case where the construction machine is not rented, a temporal stop of work for a considerable time due to the active DPF regeneration results in deterioration of general efficiency of the work process of the construction machine.
Further, since the engine needs to be continuously driven during the active DPF regeneration process continued for the long time, there is difficulty in which the amount of fuel consumption increases in proportion to a continuous time of the performance of the active DPF regeneration.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.